Employing atomic force microscopy,transmission electron microscopy and the second harmonic generation technique,we carefully explore the structural properties of 6-unit-cell-thick La_(0.8)Sr_(0.2)MnO_3 films grown on SrTiO_3 with atomically flat TiO_2-terminated terraces on the surface.The results clearly demonstrate that the terraces on the surface of TiO_2-terminated SrTiO_3 can improve the layer-by-layer epitaxial growth of the manganite films,which results in uniform film coverage at the beginning of growth and thus reduces the substrate-induced disorder at or near the interface.Comparing the magnetic and transport properties of La_(0.8)Sr_(0.2)MnO_3 films with the thicknesses varying from 6 unit cells to 80 unit cells grown respectively on as-received SrTiO_3 and TiO_2-terminated SrTiO_3,it is found that these atomically flat terraces on the surface of TiO_2-terminated SrTiO_3 can greatly enhance the Curie temperature and conductivities of the ultrathin La_(0.8)Sr_(0.2)MnO_3 films with thickness less than 50 unit cells,while no obvious difference is detected in the magnetic and transport properties of the 80unit-cell thick films. Employing atomic force microscopy, transmission electron microscopy and the second harmonic generation technique, we carefully explore the structural properties of 6-unit-cell-thick La 0.8 Sr 0.2 MnO 3 films grown on SrTiO 3 with atomically flat TiO 2-terminated terraces on the surface.The results clearly demonstrate that the terraces on the surface of TiO_2-terminated SrTiO_3 can improve the layer-by-layer epitaxial growth of the manganite films, which results in uniform film coverage at the beginning of growth and thus reduces the substrate- induced disorder at or near the interface. Comparing the magnetic and transport properties of La_ (0.8) Sr_ (0.2) MnO_3 films with the thicknesses varying from 6 unit cells to 80 unit cells grown as on-received SrTiO_3 and TiO_2-terminated SrTiO_3, it is found that these atomically flat terraces on the surface of TiO_2-terminated SrTiO_3 can greatly enhance the Curie temperature and conductivities of the ultrathin La_ (0.8) Sr_ (0.2) MnO_3 films with thickness less than 50 unit cells, while no obvious difference is detected in the magnetic and transport properties of the 80 unit-cell thick films.